The invention relates to a power belt sander.
A power belt sander of this generic type has been disclosed by GB 2 293 122, in which the power of a motor is transmitted by means of a drive roller to a sanding belt, which travels over a deflection roller spaced apart from and parallel to the drive roller. At the same time, there is frictional adhesion between the inside of the sanding belt and the deflection and drive rollers.
In order to assure the frictional adhesion between the sanding belt and the drive roller, the sanding belt traveling over the drive roller must be prestressed in relation to it with a minimum force. This is achieved by virtue of the fact that the deflection roller is supported so that it can be elastically displaced and is supported so that it is prestressed against the inside of the sanding belt. Tension elements are required for this, which attempt to press the deflection roller elastically away from the drive roller.
The slippage required for the power transmission between the drive roller and the sanding belt causes a relatively intense wear on the drive roller friction cover, which is usually made rubber. In addition, the sanding belt and the drive roller are heated relatively intensely by the slippage. This increases the tendency of the sanding agent layer to clog up and the tendency of the work piece surface to become lubricated, for example with paint residue or lacquer, which are already intensely heated anyway during the sanding. In the extreme case, surface regions of the work piece can become heat blackened.
Due to the heating and the slippage, the inside of the sanding belt becomes continuously smoother so that the service life of the sanding belt and the service the drive roller are reduced.
In addition, with the known power belt sanders, the continuous sanding belt, which is guided by frictional adhesion, must be kept in a central running position in relation to the drive roller and the guide roller by means of a complex adjusting device in order to prevent it from coming off the side of the drive roller and the deflection roller.
The power belt sander according to the Invention can be produced at a lower cost, is lighter in weight, and can be smaller in design than the known machines because the adjusting and tensioning means are no longer necessary. Moreover, the positive engagement between the drive roller and the sanding belt permits a quasi slip-free transmission of power to the sanding belt and results in an extended service life of the sanding belt and greater sanding abrasion.
Since a toothed sanding belt, as a support for the sanding belt, is guided on matched denticulations of the drive roller and deflection roller, the sanding belt does not have to be centered or elastically prestressed because even with the relatively low tension of the toothed sanding belt, the positive engagement between the drive roller and the uniform revolution of the toothed sanding belt are assured.
The slippage between the toothed sanding belt and the sanding belt can be minimized by virtue of the fact that on its back side, the toothed sanding belt supports the sanding belt so that it is secured against relative movement, e.g. by means of an adhesive connection or a hook-and-loop fastener.
Because the sanding belt is open, i.e. has two ends and does not constitute a closed ring, it is cheaper to produce and is easier to mount in abutting fashion on the power belt sander or on the toothed sanding belt.
For the case in which the toothed sanding belt has a sanding agent layer glued, vulcanized, or injection molded in place on its back side, the toothed sanding belt, with a particularly long service life, performs the function of the sanding belt, whose initial cost and installation are then rendered superfluous.
A clogging of the abutting point between the ends of the sanding belt with sanding dust is counteracted by virtue of the fact that one end of the sanding belt is thicker than the other and is disposed before the thinner end in the rotation direction of the sanding belt.
The fact that the ends of the sanding belt extend parallel to each other, diagonal to the travel direction effectively further counteracts the clogging of the impact point.
By virtue of the fact that instead of the toothed sanding belt, a V-belt or flat belt are used and instead of the drive roller and deflection roller, V-belt wheels or flat belt wheels are used, the above-mentioned advantages can be achieved in a manner similar that of a toothed sanding belt.
Because the toothed sanding belt, flat belt, or V-belt has recesses on its back side for the insertion of sanding segments, separate sanding segments can be disposed overlapping one another and can be individually replaced when they become worn.
By virtue of the fact that the tooth points of the toothed sanding belt are provided with a low-friction cover, in particular a textile cover, the toothed belt can be guided via a sliding shearing force and during sanding, is supported against this sliding shearing force so that it is possible for the sanding belt to exert a uniform distribution of force on the work piece.
The above-mentioned advantage that over its entire width or over its entire lower surface area oriented toward a work piece to be machined, the sanding belt is supported uniformly on the work piece, is improved by virtue of the fact that the sanding shoe which serves to support the sanding belt in relation to a work piece, is recessed in groove fashion in the vicinity of the toothed sanding belt so that its distance from the back side of the sanding belt and the back side of the toothed sanding belt is approximately equally small.